CVE-2023-25908 - Explaining the Use-After-Free Flaw in Adobe Photoshop and How Attackers Exploit It

Adobe Photoshop is practically the standard for digital image editing, used by millions around the world. But what many users don’t know is that even a well-polished piece of software like Photoshop can have severe vulnerabilities—like CVE-2023-25908, which can allow a criminal to take over your computer, just by convincing you to open a tainted file. This article breaks down what this vulnerability is, how it works, gives you code examples, and shows you what an exploit might look like.

What is CVE-2023-25908?

CVE-2023-25908 is a critical security hole in Adobe Photoshop versions 23.5.3 (and before) and 24.1.1 (and before) that stems from a type of bug called "Use After Free." In layman's terms, this kind of bug lets potential attackers trick Photoshop into using some memory that’s already been "freed" (no longer meant for use), which could let them run their own code on your computer—ultimately leading to things like installing malware, stealing your data, or hijacking your system.

References

- Adobe Security Bulletin APSB23-22
- NIST NVD NVDCVE-2023-25908

What’s a Use-After-Free? (With Simple Code)

A "Use-After-Free" occurs in programs written in languages like C or C++ (which Photoshop is), when the application "frees" (or deletes) a piece of memory but then keeps trying to access it later.

Here’s a super simple example in C

#include <stdio.h>
#include <stdlib.h>

int main() {
    char *data = malloc(100);   // Allocate memory
    free(data);                 // Free it

    data[] = 'A';              // <— Oops! Use After Free
    printf("%c\n", data[]);

    return ;
}

*What happens:*

Memory is freed with free(data).

- The next line tries to write to that same memory location (data[] = 'A';), which is no longer safe.

In a huge application like Photoshop, this could happen when, say, handling different image layers or effects with improper memory management.

How Is CVE-2023-25908 Exploited?

Attackers create a specially crafted Photoshop file—maybe a .PSD file with a weird, deeply nested set of image data. When a victim opens this file:

Photoshop reads and manipulates the file’s data.

2. Some internal object gets freed in memory (but isn’t properly removed from the program’s workflow).

Photoshop tries to use the freed object again, leading to ‘Use-After-Free’.

4. If the attacker controls what sits at that freed memory address, they can sneak in their own program code. Photoshop then executes that code with the same privileges as the person opening the file.

This type of bug is much easier to pull off if the software doesn’t have protection features like Address Space Layout Randomization (ASLR) properly implemented or if heap metadata can be predicted.

Here's what a (heavily simplified) heap spray exploit could look like, using a crafted .PSD file

# Attacker's script for creating a malicious PSD file (conceptual)
from psd_tools import PSDImage, Group, Layer

# Helper to create intentionally malformed layer data
def make_malicious_layer():
    # Oversized metadata or recursive structure triggers Use-After-Free internally
    return Layer(name="bad", size=(10000,10000), ...)
 
psd = PSDImage()
for i in range(100):
    # Add lots of normal layers to fill up memory
    psd.append(Layer(name=f"normal{i}", size=(100,100)))
    
# Place the malicious layer in a precise spot
psd.append(make_malicious_layer())

psd.save("evil.psd")

When evil.psd is opened in a vulnerable Photoshop, Photoshop’s code might "free" a structure (pointer), then—because of the malformed content—unexpectedly use it again. But now, its contents have been tampered with by stacking tons of layers and the attacker’s code.

Real-World Use

Researchers don’t release full working exploits for this bug (to protect users), but the above scenario is what a real attacker might do:

What Makes This Vulnerability So Dangerous?

- Just opening a file can compromise you. There’s no need for weird plug-ins, no popups, nothing.

Patch now.

Update to the latest version of Adobe Photoshop, as Adobe has released fixes.

Final Thoughts

CVE-2023-25908 is a classic "user trick" vulnerability—malicious people wait for you to do something normal (like open a file), and then zap you via a flaw deep inside your software. But knowledge is power: update your Photoshop, stay vigilant about files, and you’ll be safer from these invisible digital attacks.

Timeline

Published on: 03/27/2023 21:15:00 UTC
Last modified on: 04/03/2023 13:17:00 UTC